P1299: OUTCOMES OF YOUNG ADULTS (AGED ≤40 YEARS) WITH NEWLY DIAGNOSED MULTIPLE MYELOMA AFTER UPFRONT AUTOLOGOUS STEM CELL TRANSPLANT
Authors: Oren Pasvolsky, Curtis Marcoux, Denái R. Milton, Adeel Masood, Mark R. Tanner, Qaiser Bashir, Samer Srour, Neeraj Saini, Jeremy L. Ramdial, Yago Nieto, Hans C. Lee, Krina K. Patel, Partow Kebriaei, Priti Tewari, Sheeba K. Thomas, Donna M. Weber, Robert Z. Orlowski, Lindsay Crawford-Suber, Elizabeth J. Shpall, Richard E. Champlin, Muzaffar H. Qazilbash
Journal: HemaSphere (2023)

Topic: 22. Stem cell transplantation - Clinical Background: There is growing recognition that young adults with cancer have unique biological characteristics, clinical features, and treatment outcomes. Multiple myeloma (MM) is primarily a disease of the elderly with a median age of diagnosis between 65–70 and fewer than 2% of patients are less than 40 years of age at diagnosis. There is a paucity of data regarding adolescent and young adult (AYA) MM patients undergoing autologous hematopoietic stem cell transplantation (auto-HCT), which is standard of care for eligible patients with newly diagnosed MM. Aims: We sought to evaluate the long-term outcomes of young adult MM patients, aged ≤40 years, who underwent auto-HCT at MD Anderson Cancer Center. Methods: We conducted a single-center chart review-based analysis. We searched for MM patients 15-40 years of age who received upfront auto-HCT between 1989 to 2021. Progression free survival (PFS) and overall survival (OS) were estimated using Kaplan-Meier method and differences between groups were assessed using the log-rank test. Associations with survival outcomes were determined using Cox proportional hazards regression models. Response post transplant was included in the models as a time-dependent covariate. Results: A total of 117 patients were included in our analysis. Median age was 37 (range 22-40) years and 69 (59%) patients were male. There were 61 (52%) and 56 (48%) patients who underwent auto-HCT before and after 2010, respectively. High-risk cytogenetic abnormalities were found in 15% of the patients. As expected by the young age of the cohort, most patients had a low burden of comorbidities (HCT-CI ≤ 3, 73%). Following induction and prior to auto-HCT, 12 (10%) and 52 (44%) of patients achieved at least complete response (CR) or very good partial response (VGPR), respectively (Table 1). Median follow-up in survivors was 72.6 (range 0.9-238) months. Day 100 and best post-transplant responses were ≥CR in 32% and 56%, and ≥VGPR in 63% and 77% of patients, respectively. For the entire cohort, median PFS was 43.1 (95% CI 31.2–65.0) months and median OS was 146.6 (95% CI 100.0-208.1) months. Patients transplanted after 2010 had better median PFS [(84.9 months 95% CI 57.8-not reached (NR)) vs. (28.2 months 95% CI 20.5-41.3), p<0.001; Figure 1A] and OS [(NR 95% CI 105.6-NR) vs. (91.8 months 95% CI 56.0-146.6), p<0.001; Figure 1B] compared to those transplanted prior to 2010. In multivariable analysis, achieving ≥CR as best post-transplant response was associated with improved PFS (HR 0.56, 95% CI 0.32-0.95, p=0.033), and achieving ≥VGPR as best post-transplant response was associated with improved OS (HR 0.24, 95% CI 0.12-0.47, p<0.001). Three patients (3%) developed a second primary malignancy (colon cancer, bladder cancer and melanoma, n=1 each). Summary/Conclusion: In this single center retrospective analysis of young adult MM patients aged ≤40 years undergoing upfront auto-HCT, depth of response following transplant was associated with improved survival outcomes. Those who underwent auto-HCT in more recent years had better PFS and OS, consistent with the continued improvement in therapy for the general MM population. OS in this younger cohort following upfront auto-HCT exceeded that reported in older patients and should be considered in assessing the efficacy of novel therapies, such as CAR-T cells and bispecific antibodies.Keywords: Multiple myeloma, Autologous hematopoietic stem cell transplantation, Age